International Publication WO2008/129929 discloses a gas analyzer that uses quadrupole mass spectrometry or the like and includes: an ionizer unit that ionizes a sample gas; a first ion detection unit and a second ion detection unit that detect ions from the ionizer unit and are provided on both sides of the ionizer unit so as to be located at different distances from the ionizer unit; a filter unit that is provided between the ionizer unit and the first ion detection unit and selectively passes ions from the ionizer unit; and a calculator apparatus that uses a first total pressure of the sample gas obtained by the first ion detection unit and a second total pressure of the sample gas obtained by the second ion detection unit to correct a partial pressure of a specified component that is obtained by the first ion detection unit and selected by the filter pole unit, wherein it is possible, while maintaining the resolution, to carry out correction even in a region where the measured pressures do not track changes in the ambient pressure.
International Patent Publication WO2007/083403 discloses a quadrupole mass spectrometer in which a table for associating an appropriate DC bias voltage to each of a plurality of selectable scan speeds is stored in advance in an auto-tuning data storage unit. In an auto-tuning operation, a controller determines the DC bias voltage corresponding to each scan speed by referring to the table and fixes the output of an ion-attracting voltage generator unit at that voltage. While changing the other applied voltages such as the voltage applied to an ion optical system, the controller finds voltage conditions under which the detection signal is maximized. The optimal conditions for each scan speed are then found and recorded in auto-tuning result data. During analysis of a target sample, a DC bias voltage corresponding to a scan speed specified by the operator is obtained from the table, optimal conditions are obtained from the auto-tuning result data, and the scan measurement conditions are determined based on such information. By doing so, it is possible to prevent deterioration in the detection sensitivity when the scan measurement is performed at a high scan speed.